The invention relates to a method for controlling an antenna of an earth station for telecommunication via satellites, which antenna is provided with means to determine the position of the antenna and with means to ascertain the strength of the received signal.
Various known methods make use of the so-called hill-climbing method, so named because in this method there is a continuous search for a position of the antenna in which the received signal is stronger than it was in the preceding position; in other words: in the hilly landscape of signal strengths one always tries to climb. One of the ways to realize this method is the so-called "step-track" method. This "step-track" method is a simple and relatively cheap solution for keeping an antenna pointed at a satellite. The position of the antenna is changed step by step with equal steps of for example 0.01.degree., both in elevation and in azimuth, it being always tried to find a position in which the received signal is as strong as possible.
The tracking system using the "step-track" method causes in an arbitrary direction a step-by-step change in for example the direction of elevation. If due to this change of position the strength of the received signal measured increases, a next step is made in the same direction, and so forth. When after a number of steps a signal decrease caused by the last step is observed, then one step is made backwards, after which a similar step-by-step change of position is started in the azimuth direction. As the received signal can be subject to strong fluctuations due to atmospheric influences, measuring of the signal strength has to take place over a longer time, for example some minutes, after which the average value is determined. Each change of position of the antenna is time-consuming because of the great slowness of the antenna. Each first step is arbitrary with the risk of a decrease of signal.
The object of the invention is to overcome the drawbacks of the "step-track" method.
Another object of the invention is to provide a method in which the correction of the position of the antenna is effected in such a way that the antenna makes the smallest possible number of steps, because steps calculated beforehand as to their direction and size are made. This object is attained because the direction and the magnitude of each change of position to be made by the antenna are derived from the change of the signal strength and the attendant change of position in consequence of the uncontrolled changes of position made by the antenna with respect to the position chosen.